The present invention relates to an apparatus for receiving a stream of tablets in aligned sequence, and for moving the stream of tablets beneath a sensing head to measure a physical parameter of the tablets, and for conveying the tablet stream into two or more paths, depending upon the measured parameter. The invention is preferably usable in connection with a stream of medicinal tablets of the various types and forms made by the pharmaceutical industry.
Pharmaceutical tablets are typically made in a process which involves compressing a powdered mixture in a mold cavity to form a solid tablet construction. After forming, the tablets are sometimes coated with various coating materials, but in some cases the pressed tablets are processed without coating. The manufacturing process produces tablets of uniform size and shape, but the nature of the process inherently leads to a number of broken or partially-formed tablets, or tablet particles, or tablets which do not meet the necessary weight specifications, which must be separated from the correctly formed tablets prior to packaging. Since the tablets are typically manufactured in considerable volumes, the process of inspecting and separating good tablets from bad tablets must necessarily be a relatively high-speed process. The tablets produced by the manufacturing process are typically quite brittle in construction, and therefore the subsequent handling of tablets must be made with some degree of care in order to avoid damaging the completed tablets.
The assignee of the present invention has previously disclosed, in U.S. Pat. No. 5,135,113, issued Aug. 4, 1992, a tablet machine for sorting tablets by capacitive measurement. This patent describes a machine particularly useful for the sorting of tablets having a cylindrical shape, wherein the tablets are guided onto a rotating disk and conveyed between capacitor plates, and including a deflector assembly for deflecting tablets along one of a possible number of paths as a consequence of the capacitance measurement made by the device. The assignee of the present invention has also disclosed, in U.S. patent application Ser. No. 07/947,064, filed Sep. 18, 1992, now U.S. Pat. No. 5,240,118 a tablet sorting machine of the same general type having an apparatus for conveying tablets in uniform alignment and orientation from the peripheral edge of a rotating turntable. The present invention is usable with this form of tablet conveying device, and represents an improvement over the aforementioned patent in that the present device enables the conveying and measurement of tablets of varying shapes and sizes, including nonsymmetrical tablets.
The problem of measuring capacitive parameters of tablets under high-speed conditions requires that the tablets be uniformly and sequentially arranged, and that their alignment relative to the capacitive measuring plates be carefully controlled. When tablets such as circular tablets are measured in this way, the symmetrical design of the tablet requires only that the tablet maintain a uniform position relative to its axis while it is conveyed through the sensing device. The orientation of the tablet need only be controlled so as to maintain the axis of the tablet in a relatively vertical position while the tablet passes between the capacitive measurement plates. The measurement problem becomes compounded when tablets having nonsymmetrical dimensions are provided, for such tablets require uniform positioning along multiple axes while passing between the capacitive measurement plates.